Polymer liners have found widespread use. Large sheets of liner can be used in hazardous waste pits to protect the underlying soil from contact with the waste. Alternatively, the liners can be used to protect water supplies from contaminants, prevent vector migration from waste water, keep animals out, contain gas from digesters, and so forth. When used for this purpose, the liners are floated on the surface of the liquid. Liners are also used to cover grain stockpiles, coal and other mineral stockpiles, and even as daily covers for landfills.
Liners are produced in rolls of limited width. It is rare that the manufactured liner is as wide as the area being covered. Therefore, techniques have been developed to weld adjacent sheets of liner together. FIGS. 1, 2, and 3 illustrate a prior art method of welding adjacent liner sheets. FIG. 1 illustrates a welding machine 10 used to weld overlapping portions 2, 2a of adjacent (poly-flex liner) liners to produce a fusion-bonded poly-flex liner 7. A hot wedge 12 heats the liner portions 2, 2a so that each has a slightly melted surface. These surfaces are then pressed together by (Nip/Drive) rollers 14, allowing them to bind together and cool producing a welded seam 4 between the adjacent sheets. The welding machine 10 is pulled along manually or can be mechanized. The (double) hot wedge (or shoe) 12, shown in perspective in FIG. 2, has a generally wedged form surface that can be heated. In the model shown, two ridges 12a, 12b contact the overlapping portions of adjacent liner. Thus, a double weld is produced, as shown in FIG. 3, with a central unwelded portion (or air channel) 6, and a squeeze out 3.
Liners are subjected to wind uplift, lateral wind displacement, gas collection and inflation, storm water collection, snow loads, and other forces or combinations of the above forces which can cause significant stresses on the liner and its anchorage. Currently, these liners are held down by weighted plastic pipes, sandbags, tires tied to a rope lattice, sacks of concrete, and other passive methods. A need exists for a better way to secure welded liner in place.